mysql 游标使用

请使用 mysql 1.5 或以上version;

测试表 level ;

create   table  test. level  (name  varchar ( 20 ));

 再 insert 些数据 ;

View Code

/*初始化*/ 

 drop procedure if exists  useCursor // 

   

 /*建立 存储过程 create */ 

 CREATE PROCEDURE useCursor()

    BEGIN

    /*局部变量的定义 declare*/ 



         declare tmpName varchar(20) default '' ;



         declare allName varchar(255) default '' ;



         declare cur1 CURSOR FOR SELECT name FROM test.level ;



         /*    mysql 不知道为什么用异常加入判断 ？



          *    此请参考官方文档 20.2.11. 光标 光标 



          *        这把 游标 异常后 捕捉 



          *        并设置 循环使用 变量 tmpname 为 null 跳出循环。



          */



         declare CONTINUE HANDLER FOR SQLSTATE '02000' SET tmpname = null;

  



    /*开游标*/ 



     OPEN cur1;



         /*游标向下走一步*/ 



         FETCH cur1 INTO tmpName;



         /* 循环体 这很明显 把游标查询出的 name 都加起并用 ; 号隔开 */



      WHILE ( tmpname is not null) DO



          set tmpName = CONCAT(tmpName ,";") ;



          set allName = CONCAT(allName ,tmpName) ;



        /*游标向下走一步*/ 



        FETCH cur1 INTO tmpName;



      END WHILE;



      CLOSE cur1;





    select allName ;



END;//



call useCursor()//

运行结果： 

View Code

mysql> call useCursor()//



+--------------------------------------+



| allName                              |



+--------------------------------------+



| f1;c3;c6;c5;c2;c4;c1;f1;f3;f4;f2;f5; |



+--------------------------------------+



1 row in set (0.00 sec)

View Code

DELIMITER $$  

  

DROP PROCEDURE IF EXITS cursor_example$$  

CREATE PROCEDURE cursor_example()  

     READS SQL DATA  

BEGIN  

     DECLARE l_employee_id INT;  

     DECLARE l_salary NUMERIC(8,2);  

     DECLARE l_department_id INT;  

     DECLARE done INT DEFAULT 0;  

     DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees;  

     DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;  

  

     OPEN cur1;  

     emp_loop: LOOP  

         FETCH cur1 INTO l_employee_id, l_salary, l_department_id;  

         IF done=1 THEN  

             LEAVE emp_loop;  

         END IF;  

     END LOOP emp_loop;  

     CLOSE cur1;  

END$$  

DELIMITER ; 

View Code

/*创建过程*/

DELIMITER //

DROP PROCEDURE IF EXISTS test //

CREATE PROCEDURE test()

BEGIN

    DECLARE done INT DEFAULT 0;

    DECLARE a VARCHAR(200) DEFAULT '';

    DECLARE c VARCHAR(200) DEFAULT '';

    

    DECLARE mycursor CURSOR FOR SELECT  fusername FROM uchome_friend;

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;

    

    OPEN mycursor;

    

    REPEAT 

        FETCH mycursor INTO a;

        IF NOT done THEN

            SET c=CONCAT(c,a);/*字符串相加*/

        END IF;

        

    UNTIL done END REPEAT;

    

    CLOSE mycursor;

    

    SELECT c;

END //

DELIMITER ;